Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells per device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module having a plurality of battery cells electrically connected to one another because high power and large capacity are necessary for the middle or large-sized devices.
Preferably, the middle or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing costs of the pouch-shaped battery are low, and it is possible to easily modify the shape of the pouch-shaped battery.
Battery cells constituting such a middle or large-sized battery module may be secondary batteries which can be charged and discharged. Consequently, a large amount of heat is generated from such high-power, large-capacity secondary batteries during charge and discharge of the batteries. In particular, the laminate sheet of each pouch-shaped battery widely used in the battery module has a polymer material exhibiting low thermal conductivity coated on the surface thereof with the result that it is difficult to effectively lower overall temperature of the battery cells.
If the heat, generated from the battery module during charge and discharge of the battery module, is not effectively removed from the battery module, the heat accumulates in the battery module with the result that deterioration of the battery module is accelerated. According to circumstances, the battery module may catch fire or explode. For this reason, a middle or large-sized battery pack for vehicles, which is a high-power, large-capacity battery including a plurality of middle or large-sized battery modules, needs a cooling system to cool battery cells mounted in the battery pack.
Each battery module mounted in a middle or large-sized battery pack is generally manufactured by stacking a plurality of battery cells with high integration. In this case, the battery cells are stacked in a state in which the battery cells are arranged at predetermined intervals such that heat generated during charge and discharge of the battery cells can be removed. For example, the battery cells may be sequentially stacked in a state in which the battery cells are arranged at predetermined intervals without using an additional member. Alternatively, in a case in which the battery cells have low mechanical strength, one or more battery cells may be mounted in a cartridge to constitute a unit module, and a plurality of unit modules may be stacked to constitute a battery module. The cartridge increases the mechanical strength of the battery cells; however, the cartridge also increases the overall size of the battery module.
In addition, coolant flow channels are defined between the stacked battery cells or between the stacked battery modules such that heat accumulated between the stacked battery cells or between the stacked battery modules is effectively removed.
In particular, in a case in which the cooling structure is based on a water cooling type cooling system, a coolant conduit extends through an integrated thermal conduction member.
Specifically, there is used a cooling member having a structure in which a heat sink connection portion connected to a pipeline is formed in a protruding shape in order to inject a coolant into a flow channel defined in a heat sink and then the heat sink connection portion is inserted into the pipeline by force fitting.
In a case in which the cooling member with the above-stated construction has a plurality of pipelines, however, it is difficult to insert the heat sink connection portion into the respective pipelines by force fitting. Furthermore, the coolant may leak from fastening regions between the heat sink connection portion and the respective pipelines.
Consequently, there is a high necessity for a cooling member which effectively prevents leakage of a coolant, ensures long-term durability, and can be manufactured with improved assembly efficiency and a battery module of excellent safety using the cooling member.